U.S. Pat. No. 4,889,602 discloses an alkaline zinc-nickel electroplating bath, which comprises an aliphatic amine or polymer of an aliphatic amine in combination with an hydroxyaliphatic carboxylic acid.
U.S. Pat. Nos. 4,071,418 and 4,071,419 disclose the combination of amines with substituted pyridines, such as nicotinic acid or nicotinamide for a zinc bath.
U.S. Pat. No. 5,417,840 discloses an alkaline zinc-nickel plating bath comprising the combination of a polyamine, such as polyethyleneimine, in combination with an aromatic heterocyclic nitrogen containing compound such as a sulfo-betaine, (e.g., pyridinium-N-propane-3-sulfonic acid); or a pyridinium chloride, such as N-carboxymethylpyridinium chloride.
U.S. Pat. Nos. 4,210,500 and 4,730,022 disclose the use of an aromatic carboxyl compound such as 1-benzyl-pyridinium-3-carboxylate or 3-pyridine carboxylic acid (nicotinic acid) as a supplementary brightener in an alkaline zinc bath. The carboxyl compounds are used in combination with a primary brightener, such as the reaction product of a polyamine and a sulfonate.
U.S. Pat. No. 5,405,523 discloses a zinc alloy electroplating bath comprising a ureylene quaternary ammonium polymer as a brightening agent. The quaternary ammonium polymer can include units of the general formula:
where A may be O, S, or N, and R may be, inter alia, methyl, ethyl, or isopropyl. In the preferred polymers, these units are linked by units derived from, for example, a bis(2-haloethyl)ether, a (halomethyl)oxirane or a 2,2′-(ethylenedioxy)-diethylhalide.
U.S. Pat. No. 5,435,898 describes polymers for use as additives in the electrodeposition of zinc and zinc alloys. The polymers have the general formula:
where R1 to R4 may be the same or different and are, inter alia, methyl, ethyl, or isopropyl and Y may be S or O, and R5 is an ether linkage, such as (CH2)2O(CH2)2.
U.S. Pat. No. 6,652,728 describes polymers for use as additives in the electrodeposition of zinc or zinc alloys. The polymers have the general formula:

U.S. Patent Application Publication No. 2003/0192785 describes an additive for zinc or zinc alloy electroplating bath medium. The additive comprises a random copolymer comprising the reaction product of one or more ditertiary amines including an amide or thioamide functional group, and optionally one or more saturated or unsaturated ditertiary amines with one or more saturated or unsaturated linking agents capable of reacting with the ditertiary amines.